The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Due to today's high oil prices and strict emission regulations, automakers have been developing technologies that can enhance fuel efficiency in an environmentally friendly way.
Improvement of the fuel efficiency in an automatic transmission can be achieved through enhancement of power transmission efficiency. Likewise, improvement of power transmission efficiency can be implemented by reducing unnecessary consumption power of an oil pump.
However, in the related art, a system is configured in a way that oil pressure pumped in a mechanical pump is controlled by a pressure control valve and the oil pressure is distributed to each transmission unit. With this system configuration, flow rate cannot be controlled, and unnecessary power loss may occur.
Particularly, power loss that is caused by unnecessary oil pressure in a high RPM region may still occur, thereby reducing the fuel efficiency.
The above information disclosed in this section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.